1. Field of Invention
The present invention relates to a method for manufacturing ferrocenyl-1,3-butadiene. More particularly, the present invention relates to a ferrocenyl-1,3-butadiene synthesis method with a relatively high yield and low pollution.
2. Description of Related Art
In U.S. Pat. Nos. 3,739,004 and 3,843,426, it has been found that ferrocenyl-1,3-butadiene is an important starting material for manufacturing copolymer and homopolymer and is employed in applications such as the coating material for aerospace transportation to enhance resistance to photo degradation, ultraviolet rays and gamma rays. Ferrocenyl-1,3-butadiene also can be employed as an enhancement fuel in solid propellant. The fuel of the solid propellant comprises aluminum powder and ammonium perchlorate. Additionally, ferrocenyl-1,3-butadiene not only can be an enhancement fuel in solid propellant but also can decrease binder use. Moreover, ferrocenyl alkenes can be employed in electronic materials.
Several processes to synthesize ferrocenyl-1,3-butadiene have already been proposed. However, the prior techniques possess several disadvantages that decrease the yield and the probability of increasing the throughput. The first method for synthesizing ferrocenyl-1,3-butadiene is the method utilizing Wittg reaction as shown in the following equation (I): ##STR1##
The disadvantage of the method described above is that the reactant, allyltriphenylphosphonium bromide, is ten times more expensive than allyl bromide and the throughput of the ferrocenyl-1,3-butadiene produced by this method is only 52%. Incidentally, the by-product, Ph.sub.3 PO will not be easily removed and remains in the product.
The second method for synthesizing ferrocenyl-1,3-butadiene utilizes allyllithium as reagent and the equation of the method is indicated as equation (II) as shown below: ##STR2##
The method described above comprises two steps. First of all, allyllithium is synthesized by allyl bromide. Then, ferrocenyl-1,3-butadiene is formed in dehydration conditions of high temperature and low pressure. This is not a proper way to obtain a high throughput of ferrocenyl-1,3 -butadiene.
The third method for synthesizing ferrocenyl-1,3-butadiene utilizes allylmagnesium bromide as a synthesis reagent and the equation of the method is indicated as equation (III) as shown below: ##STR3##
The method described above also comprises two steps. In the dehydration reaction in the second step, if cupric sulfate is used as a dehydration reagent, the dehydrated water should be collected by the Dean-Stark distillatory. However, the throughput of ferrocenyl-1,3-butadiene in this method is just about 50-60% and cannot even be handled. If acidic aluminum oxide is used as a dehydration reagent, the use of aluminum oxide is ten times higher than that of the reagent. Hence, extending the throughput of ferrocenyl-1,3-butadiene by this method is improper.
The fourth method for synthesizing ferrocenyl-1,3-butadiene uses graphite-supported active zinc as a reagent and the equation of the method is indicated as equation (IV) as shown below: ##STR4##
The reagent is not a commercially available product. When preparing the reagent, potassium should be heated to a melting state, and then the melted potassium is powdered and mixed with graphite. After that, the mixture described above is used to reduce the anhydrous zinc chloride into ultra-fine active zinc powder. Usually, the throughput of ferrocenyl-1,3-butadiene reaches 85%. But if the active zinc powder is not fine enough, the yield is decreased. Therefore, it is hard to control the condition for synthesizing ferrocenyl-1,3-butadiene by using this method. Additionally, potassium is a highly active metal. If the operation is improperly or carelessly performed, an explosion is easily induced. Therefore, extending the throughput of ferrocenyl-1,3-butadiene by this method is improper.